Electricity Flashcards
Electrical charge and current
What is current?
The flow of electrical charge. It is measured with an ammeter placed in series and is measured in amps.
Electrical charge and current
What is charge?
The rate of flow of electrons. Charge is measured in coulombs. 1 coulomb = 6.25 x 10^18 electrons
Current, resistance and potential difference
What is potential difference?
The difference in energy per coulomb of charge between two points in a circuit. It is measured with a voltmeter placed parallel to the component and is measured in volts
Current, resistance and potential difference
What is an ohmic conductor?
A conductor for which current and potential difference are directly proportional. Resistance remains constant as current changes and the temperature must be constant.
Current, resistance and potential difference
What is resistance?
When electrons move through the metal and bump into the ions, slowing them down. It is measured in ohms
Series and parallel circuits
Describe series circuits.
In a series circuit, there is only one loop for current to travel through. If one of the componenets breaks, the circuit is incomplete.
Series and parallel circuits
Describe parallel circuits.
In parallel circuits, there are multiple loops for current to flow through. If one component breaks, the others may still work.
Series and parallel circuits
Describe current in series and parallel circuits.
- In a series circuit, current is the same everywhere
- In a parallel circuit, current is shared across each component
Series and parallel circuits
Describe potential difference in series and parallel circuits.
- In a series circuit, potential difference is shared across each component
- In a parallel circuit, potential difference is the same everywhere
Series and parallel circuits
Describe resistance in series and parallel circuits.
- If placed in series, the resistances are added together
- If placed in parallel, the resistance is reduced
Direct and alternating potential difference
What is direct current? (d.c.)
Flows in only one direction
Direct and alternating potential difference
What is alternating current? (a.c.)
Current that regularly changes direction
Mains electricity
Describe the mains electricity supply.
The supply is generated at a frequency of 50 Hz and is delivered to houses at 230 V
Mains electricity
What are the three wires usually in the cables connecting electrical appliances to the mains?
- Earth wire - green and yellow - safety wire, connects to the earth in case of a fault
- Live wire - brown - carries the a.c.
- Neutral wire - blue - completes the circuit
Power
What is power measured in?
Watts
The national grid
What is the national grid?
The National Grid distributes electricity across the country. It connects power stations to homes, workplaces and public buildings all around the country.
The national grid
Describe the importance of transformers.
In order to ensure that less energy is lost through heating the wire, step up transformers increasethe voltage to decrease the current. However, high voltage is very dangerous, so before reaching the end user, a step down transformer reduces the voltage to a safer amount for home use.
Static charge
What can happen when insulating materials are rubbed together?
They become electrically charged
Static charge
Why can insulators become electrically charged when rubbed together?
- Electrons are rubbed from one material to another
- The material gaining electrons becomes negatively charged
- The material losing electrons becomes postively charges
Static charge
What happens when two electrically charged objects are brought closer together?
The exert a force on each other.
Static charge
What happens when two identically charged or oppositley charged objects are brought close together?
- Identically charged - exert a repulsive force on each other and repel
- Oppositely charge - exert an attractive force on each other and attract
Static charge
What is discharging and how does it work?
As an electric charge builds on an object, the potential difference between the object and the earth increases.
The air surrounding can become ionised due to the high p.d, so electrons can jump across the gap between the object and the earth to any earthed conductor.
Electric fields
What are electric fields?
A charged object creates an electric field around itself. This is an area that exerts a force on other charged objects and is strongest closest to the object.
